Battery Basics

Introduction

As battery powered device increasing in ubiquity, system EE need to have solid understand of battery chemistry, capacity, aging, and charging and discharged curve.

Overview

  • Chemistry

    • Lithium ion/LIPO/Lithium Polymer - Rechargeable

      • Operating voltage: ~ 3V to 4.2V

    • Alkaline

      • Operating voltage: 0.9V to 1.5V

    • Nickel–cadmium battery (NiCD)

      • 1.2V nominal

    • Nickel-Metal Hydride (NiMH)

      • 1.2V nominal

  • Capacity (measured in mAh)

    • Lithium ion

      • ~ 3000 mAh for a typical phone

    • Alkaline

      • ~1000 mAh for AAA battery

    • Nickel–cadmium battery (NiCD)

      • 1000 mAh

    • Nickel-Metal Hydride (NiMH)

      • 2500 - 2700 mAh

  • Energy Density

    • Volume Metric Density (measured in W-HR/L)

      • Lithium Ion: 210

      • Nickel–cadmium battery (NiCD): 140

      • Nickel-Metal Hydride (NiMH) : 180

  • Charging Rate

    • Measured in C

      • 1 C means it takes an hour to finish chaging from 0% to 100%; 2C means it takes 30 mins to finish charging.

  • Charging Curve

    • Lithum ion

      • Precharge/Trickle charging (Vbat < 2.1V) -> Constant Current -> Constant Voltage (taper off at vbat ~ 4.35V) -> Charging termination (0.02C)

        • termination is based on charging current falling below a threshold rate, typically 0.02C to 0.07C

    • Nickel-Metal Hydride (NiMH)

      • Trickle charging -> Constant Current -> top-off charge -> Charging termination

Q&A

Why is Lithium Ion battery chosen for premium portable electronics such as a smart phone?

    • Lithium Ion battery has the highest energy density.

References and Further Reading:

" Recharging Alkaline Batteries : Fact or Fiction?", https://zbattery.com/Recharging-Alkaline-Batteries-Fact-or-Fiction

"Battery Energy Density": https://forum.digikey.com/t/battery-energy-density/445?utm_adgroup=Battery%20Products&utm_source=google&utm_medium=cpc&utm_campaign=Dynamic%20Search_RLSA_Buyers&utm_term=&utm_content=Battery%20Products&gclid=CjwKCAjwjqT5BRAPEiwAJlBuBdy6wksR42v3cfwgH-gFmsifrNk9z1xg_K82YEDWmiR_GsrXdBnqmhoCfDoQAvD_BwE

"Battery Charging", https://www.ti.com/lit/an/snva557/snva557.pdf?ts=1596610924925&ref_url=https%253A%252F%252Fwww.google.com%252F

"Charging Lithium-ion", https://batteryuniversity.com/learn/article/charging_lithium_ion_batteries#:~:text=Figure%203:Volts/capacity%20vs.%20time%20when%20charging%20lithium-ion.%20The%20capacity%20trails

"Developing Affordable Mixed Signal power ysstems for Battery Charger Applications", http://www.rusmagnet.ru/2019/MANUALS/en027883.pdf